1. Field of the Invention
The present invention relates to a metal gate structure and a method of making the same, and more particularly to a method of forming a metal gate structure which has metal gates in the iso region which are higher than metal gates in the dense region.
2. Description of the Prior Art
With the trend towards miniaturization in the semiconductor industry with corresponding improvements in semiconductor manufacturing processes, manufactures are able to form both dense regions and iso regions on one chip.
During an etching process, because the iso regions have larger openings at the surface area than dense regions, the etchant will contact and react with more objective material in the iso regions. Consequently, the etching rate is higher in the iso regions, and more by-products are produced. This can cause gate patterns in the iso regions to be over etched, in some cases, even exposing the material layer within iso regions under gate patterns, which is undesirable.